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Quality of Service Issues in Multi-Service Wireless Internet Links

Quality of Service Issues in Multi-Service Wireless Internet Links. George Xylomenos and George C. Polyzos Department of Informatics Athens University of Economics and Business Athens 10434, Greece polyzos@aueb.gr http://dias.aueb.gr/~gcp/ Tel.: +30-1-8203-650, Fax: +30-1-8203-325. Outline.

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Quality of Service Issues in Multi-Service Wireless Internet Links

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  1. Quality of Service Issuesin Multi-ServiceWireless Internet Links George Xylomenos and George C. Polyzos Department of Informatics Athens University of Economics and Business Athens 10434, Greece polyzos@aueb.gr http://dias.aueb.gr/~gcp/ Tel.: +30-1-8203-650, Fax: +30-1-8203-325

  2. Outline • Motivation • Wireless systems and Internet applications • TCP throughput degradation • UDP and real-time application issues • Proposed approaches • Flexible Link Layer Internet Protocol (FLLIP) • Multi-protocol, adaptive, QoS/DS aware solution • Goals, architecture, implementation • Implicit and explicit service selection • Conclusion polyzos@aueb.gr

  3. Modern Wireless Systems • Opportunities and issues • Digital wireless systems • Cellular, PCS, 3G • Wireless LANs • LEO/MEO Satellites, LMDS • Mobility • Internet protocols: designed for networks that were • Wired: low error rate • TCP:loss  congestion • Fixed: no mobility, no handoffs • Physical layer solutions • Inflexible: one size fits all polyzos@aueb.gr

  4. Internet Applications and Protocols • Conventional data exchange applications • Usually TCP based • Error intolerance • Delay tolerance • Jitter intolerance (TCP) • Interactive and real-time applications • Often UDP based (plus RTP) • Often multipoint (IP Multicast) • Some error tolerance • Delay intolerance polyzos@aueb.gr

  5. Proposed Approaches • Indirect TCP • violation of semantics (not end-to-end anymore) • Snoop TCP • works well only in the direction towards the mobile • Modifications to TCP • Compatibility: usually both ends need to be updated • End-to-end retransmissions for a local problem • Not multi-protocol: useless for non TCP applications • Conventional link-layer schemes • Inflexible: one service only • Irrelevant for some protocols/applications polyzos@aueb.gr

  6. TCP/UDP TCP/UDP TCP/UDP IP IP IP IP 2Mbps 10Mbps 2Mbps LL LL LL LL 3ms 1ms 3ms PHY PHY PHY PHY Wireless Host A Base Station A Base Station B Wireless Host B Simulation Experiments • One and two wireless link scenarios • Exponential intervals between errors • 0.8-5.9% frame loss rates (1 Kbyte frames) • TCP: 100 Mbyte file transfer • UDP: Voice activated CBR video (1 Mbps) • Each test repeated 30 times polyzos@aueb.gr

  7. TCP Performance: Throughput polyzos@aueb.gr

  8. UDP Performance: Delay polyzos@aueb.gr

  9. Flexible Link Layer Internet Protocol (FLLIP) • Address the problem at its source • Local solution to a local problem • Compatible with Internet protocols & architecture • IP and higher layers unchanged • Aware of QoS requirements • Implicitly or explicitly • Per stream or classQoS differentiation • Fully or mostly reliable • Dynamic adaptation to stream/class mix • Variable bandwidth allocation • Dynamic adaptation to channel conditions polyzos@aueb.gr

  10. FLLIP Architecture • Multiple link layer modules • Packet classifier • Protocol, TCP/UDP ports • IP ToS, DS field • Per class load measurements • Incoming bandwidth allocations • Service class specific processing • Isolation between services • Frame scheduler (SCFQ) • Enforces incoming bandwidth allocations polyzos@aueb.gr

  11. SCFQ Frame Scheduler • Enforces incoming allocations • Protects services • Encourages efficiency • Self-clocked fair queueing (SCFQ) • Efficient, simple, fair • One queue per class • Heap sort polyzos@aueb.gr

  12. TCP Performance: Throughput with FLLIP polyzos@aueb.gr

  13. UDP Performance: Delay with FLLIP polyzos@aueb.gr

  14. Service Selection • Implicit QoS specification • Assigns applications to services • Protocol and TCP/UDP port fields • No changes to Internet protocols and applications • Immediate applicability • Explicit QoS specification • Assigns traffic classes to services • QoS provision • Integrated Services, RSVP • QoS differentiation • Differentiated Services • More flexible polyzos@aueb.gr

  15. Heuristic Packet Classifier • Implicit QoS specification polyzos@aueb.gr

  16. Differentiated Services Packet Classifier • Explicit QoS specification • Dynamic service selection polyzos@aueb.gr

  17. Service Measurement and Mobility Feedback • Service selection • Standard metrics • Refinement • Adaptive applications • Mobility polyzos@aueb.gr

  18. Conclusions • TCP performance severely impacted by wireless losses • TCP is not the only concern • Real-time multimedia over UDP • New applications and protocols • Link layer enhancements • Fast local recovery • Customized to underlying link • Wireless links: natural choice to introduce • QoS support • Differentiated services because • Bandwidth is scarce and expensive • Link performanceis variable and unpredictable polyzos@aueb.gr

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